Resumo

RODRIGUEZ-VALENCIA, J.A. Response of benthic polychaetes to environmental variability and El Niño conditions at Petacalco Bay (Guerrero, Mexico). Cienc. mar [online]. 2004, vol.30, n.4, pp.585-594. ISSN 0185-3880.

Fluctuations of temperature, salinity, and dissolved oxygen in the superficial (0-7 m) and lower (7-23 m) layers of the water column in Petacalco Bay (Guerrero, Mexico) and their effects on benthic polychaetes were analyzed on different dates between 1992 and 1994. Samplings undertaken during 1992 allowed the detection of the terminal phase of the 1992 El Niño event, followed by the discharge of warm freshwater from a power plant (2100 MW) over the surface of the bay. During the 1992 El Niño, the water was significantly warmer, more saline, and contained more oxygen than during 1993-1994. Stratification of the water column increased after the dissipation of El Niño conditions, and dissolved oxygen and salinity levels decreased noticeably. Polychaete abundances and the number of species were lowest during the El Niño period and increased afterwards. These changes occurred despite the operation of the power plant, since its discharges remained on the surface of the bay. Emersions of deep water through the Petacalco submarine canyon in spring may also have had a positive effect.

Palavras-chave : Petacalco Bay; polychaetes; El Niño; Guerrero; Mexico.

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